Thr present invention relates generally to the field of devices for controlling transmission gear shift selection and, more specifically, to such devices which effect gear shift change based upon engine rotational speed (RPMs).
Automotive vehicles equipped with automatic or semi-automatic transmissions are typically equipped with a manually operable gear shift selection lever which permits the operator to place the vehicle in various operational modes, such as forward, reverse, neutral and park. Usually, in the forward drive mode, there are at least two or three drive settings. While vehicles having fully automatic transmissions can be driven without further manual shifting by selecting the highest drive setting, the lower drive positions allow the operator to use lower gear ratios which provide improved performance when unusual road or load conditions are encountered.
Some drivers, however, also use the lower shift positions in accelerating the vehicle from a stopped or nearly stopped position in a manner similarly to fully manual gear shifting. Thus, such a driver will start in the lowest drive position and successively shift to the second lower and highest drive positions as vehicle speed is increased. This manner of driving is also employed by race car drivers, notably dragsters.
In drag racing, automatic or semi-automatic transmissions are employed because they reduce the time needed to shift gears by eliminating manual clutching. Obviously, in order to win at drag racing, the driver must be able to initiate gear shiftig at the precise moment the optimal engine RPM speed is attained. While a tachometer gauge is provided to assist the driver in determining when to shift, the gauge can give somewhat false readings due to vehicle vibrations.
In order to further aid the drag racing driver in shifting at the right time, and indicator light is often provided which signals when the dirver should initiate the next gear shift. Obviously however, there is a significant time lapse corresponding to the driver's reaction time which is undesirable. While the indicator light can be made to compensate for the dirver's reaction time, this reaction time is not constant and therefore cannot be precisely compensated. In any event, the driver must take one hand off the steering wheel to initiate a change in gears, and must also take his eyes off the road to monitor the tach and indicator light. This is undesirable from the standpoint of insuring a proper course and control of the vehicle.